1. Field of the Invention
The present invention relates generally to an apparatus for controlling fluid flow, and specifically to a floating ball check valve for a shipboard fuel tank sounding tube.
2. Prior Art
Large ships, particularly aircraft carriers, require numerous shipboard fuel tanks to service the ship, other vehicles, and equipment. A shipboard fuel tank requires a sounding tube through which depth sounding rods and sampling instruments may be passed to measure fuel levels, sample fuel for contamination, and monitor tank bottom water and sediment. The sounding tube therefore requires an unobstructed passage for insertion and removal of these depth sounding rods and sampling instruments.
Current sounding tubes for shipboard fuel tanks are potential safety hazards. Shipboard fuel tanks are filled using high pressure fuel lines. When a tank approaches full level, fuel tends to stream up the sounding tube and overflow therefrom. The sounding tube terminals are typically located in machinery spaces, away from the fuel intake. An overflow can therefore result in a spill in the order of hundreds of gallons before the spill is detected and corrective action is taken. These fuel spills, particularly highly flamable jet fuel spills in machinery spaces, create a substantial safety hazard.
To reduce the potential safety hazard of fuel spills, the sounding tubes of the prior art are typically capped. The most common cap design is a threaded cap screwed directly onto the sounding tube terminal. The cap is removed to allow unobstructed access for sounding and sampling, and securely replaced during normal ship operations. These screw caps often seize, or fuse, as contaminants (salt, sediment, etc.) tend to lodge within the threads. Secured screw caps also prevent venting of excess tank gas pressure, which increases the safety risk. These caps further require positive action by ship personnel, and during adverse operating conditions (eg. during heavy storm conditions and during combat status on military ships), replacement of sounding tube caps receives low priority. Screw caps are therefore often left unused, misused, or lost, thereby negating the intended safety enhancement.
Sounding tube caps having other closure designs (eg. quick release catches, friction fit, etc.) are also known in the prior art. These designs are subject to substantially similar drawbacks.
For these and other reasons, the sounding tube designs of the prior art are unsatisfactory. A need exists for an improved sounding tube design having an inherent anti-spill safety feature.